1. Field of the Invention
The present invention relates to a digital recording device, a digital recording method, a program, and a storage medium, and for example to a digital recording device, a digital recording method, a program, and a storage medium that can continuously store sound such as voice or the like.
2. Description of the Related Art
The storage capacity of general-purpose memories has recently been increasing at a tremendous pace. Against a background of limitations of memory capacity thus being removed, things that have been processed in analog form in the past are being digitized daily. For example, there has been a shift from a recording method that records an audio signal of voice or the like as an analog signal as it is to a recording method that once converts an audio signal into a digital signal and stores the digital signal in a high-capacity memory. A digital audio signal thus recorded digitally is free from storage medium degradation in sound quality with the passage of time, and allows a high-speed digital transfer to be used when duplicates are made.
In a digital recording device, there is a limit to quantization accuracy, and therefore where to set a dynamic range as a recording range becomes a problem. When the dynamic range is set too low, a high sound volume exceeding the dynamic range, that is, a high sound volume higher than 0 dB causes saturation in an AD (Analog to Digital) converter, so that sound quality cannot be ensured. When the dynamic range is set high, low-level sound cannot be picked up, and thus necessary audio signals may be lost.
As a measure to solve the above problem, a technique is known which uses an AD converter having a wide dynamic range and changes stepwise a limiter characteristic or an attenuation characteristic according to input level (for example Japanese Patent Laid-Open No. Hei 8-55428). Such a technique shifts stepwise an input signal according to change in input level, and can thereby maintain sound quality even for a high sound volume input.